Copper base composition

ABSTRACT

A COPPER-MAGNESIUM-PHOSPHORUS ALLOY (OPTIONALLY CONTAINING SILVER AND/OR CADMIUM) WHEREIN THE MAGNESIUM IS PRESENT IN AMOUNTS FROM 0.01 TO 5.0 WEIGHT PERCENT, THE PHORPHORUS FROM 0.002 TO 4.25 WEIGHT PERCENT WIT COPPER MAKING UP THE REMAINDER. WHEN SILVER OR CADMIUM ARE EMPLOYED, THEY ARE EMPLOY IN AMOUNTS OF FROM 0.02 TO 0.2 WEIGHT PERCENT AND FROM 0.01 TO 2.0 WEIGHT PERCENT, RESPECTIVELY. THESE ALLOYS HAVE UNEXPECTEDLY GOOD COMBINATIONS OF MECHANICAL HEAT RESISTANCE AND CONDUCTIVITY PROPERTIES.

July 18, 1972 HNLAY ETAL 3,677,745

COPPER BASE COMPOSITION Filed Feb. 24, 1969 FIG. I

ZLL// INVENTORS WXFM United States Patent flice 3,677,745 Patented July 18, 1972 3,677,745 COPPER BASE COMPOSITION Walter L. Finlay, New York, N .Y., and Henry J. Fisher, Wellesley Hills, and Donald A. Hay, Medfield, Mass., assignors to Cooper Range Company, New York, N.Y.

Filed Feb. 24, 1969, Ser. No. 802,330 Int. Cl. C22c 9/00 U.S. Cl. 75153 10 Claims ABSTRACT OF THE DISCLOSURE A copper-magnesium-phosphorus alloy (optionally containing silver and/or cadmium) wherein the magnesium is present in amounts from 0.01 to 5.0 weight percent, the phosphorus from 0.002 to 4.25 weight percent with copper making up the remainder. When silver or cadmium are employed, they are employed in amounts of from 0.02 to 0.2 weight percent and from 0.01 to 2.0 weight percent, respectively. These alloys have unexpectedly good combinations of mechanical heat resistance and conductivity properties.

BACKGROUND OF THE INVENTION The present invention relates to copper-base alloys and more particularly to the copper-magnesium family of alloys.

As is well known, various copper base alloys have been developed in an attempt to satisfy the need for high thermal and electrical conductivity alloys having good mechanical properties and/or characteristics over a rather wide range of temperatures. Exemplary of the copper based alloys developed to satisfy this need are the copperzirconium family of alloys, disclosed in U.S. Pat. Nos. 2,842,438; 2,847,303; 3,019,102; 3,107,998 and 3,194,655. Each of these alloys was developed for a specific purpose and, in general, each of them has performed satisfactorily when used for its intended purpose. However, each of them, like most other materials, has certain shortcomings and these shortcomings militate against their use for some high volume, commercial applications where cost is an important consideration, e.g., automotive radiators. For example, with the exception of the alloys disclosed in U.S. Pat. No. 2,847,303, each of the other alloys is advantageously prepared from the copper which is substantially devoid of oxygen, e.g., oxygen free copper or copper prepared in an inert atmosphere or a vacuum. Alloys prepared from such high purity coppers are relatively expensive which seriously inhibits their use for many applications, particularly in high volume industries such as the automotive industry or electrical conductor industry where cost per unit is very important.

The alloys disclosed in U.S. Pat. No. 2,847,303 are similarly disadvantageous. For example, the copper-zirconium alloys containing phosphorus described therein do not consistently exhibit good conductivity characteristics when produced in accordance with the usual commercial methods since the amount of phosphorus added to the melt must be stoichiometrically related to the amount of oxygen present in order to prevent an excess of phosphorus in the alloy. If too much is used, the strength of the alloy may be reduced. If too little is used, complete deoxidation is not achieved. Consequently, industry, when melting phosphorus containing copper-zirconium alloys, has been faced with the difficult problem of carefully controlling the oxygen content of the charge. These controls are clearly objectionable from a practical or economic standpoint.

Of course, it has been possible to produce high strength copper alloys Without using high purity starting materials or without purging the oxygen from impure starting ma terials with phosphorus but the resultant alloys gain their increased strength only at the expense of their conductivity. Consequently, when the strength of these alloys is developed to the point where the materials fabricated from the alloy will withstand the stresses of handling and use, the conductivity of the alloy may be decreased significantly. For example, one of the largest uses for high strength copper is in the fabrication of automobile radiators and electrical components. The thin fins of the radiators are easily deformed during assembly of the radiator and of the automobile. The automobile companies, therefore, are requiring high strength alloys for use in radiator construction. Strength, however, is not the only criterion; copper alloys for use in automobile radiators must possess high thermal conductivity, i.e., preferably above 95% IACS and at least above IACS (a direct correlation exists between electrical and thermol conductivity). An inexpensive alloy having good mechanical properties at room and elevated temperatures and after exposure to elevated temperatures together with good conductivity is, therefore, greatly needed.

Although attemps have been made to provide such an alloy, none, as far as we are aware, has been entirely successful when carried into practice commercially on an industrial scale. Furthermore, it is very important in the automotive industry as well as in the aerospace industries, where metals are usually joined by welding, brazing or soldering, that as noted previously the alloy be capable of withstanding high temperature without softening appreciably.

It has now been discovered that inexpensive coppermagnesium-phosphorus alloys having excellent mechanical properties in combination which unexpected but desirable high conductivities, typically between 90 and 94% IACS in the cold-rolled condition and from about 95 to approximately 98 or even 99% in the properly thermomechanically treated condition may now be economically produced. It is an object of the present invention to provide such alloys.

The high strength and conductivity properties of the alloys of the present invention make them, in addition to radiator fins, particularly useful for the production of electrical components such as bus bars or resistance welding electrodes such as welding tips or welding wheels, and the like.

The alloys of the present invention provide inexpensive copper-magnesium-phosphorus alloys having good mechanical properties and/or characteristics and heat resistance together With good conductivities over a wide range of temperatures. The alloys of the present invention advantageously also contain silver and/or cadmium and such alloys are considered to be part of this invention and the expression "copper-magnesium-phosphorus alloy when used generically is meant to include alloys containing silver and/or cadmium.

These new copper-magnesium-phosphorus alloys comprised of a unique combination of ingredients, in special proportions, when properly thermo-mechanically processed, are characterized by being resistant to softening after being exposed for normal soldering cycles to temperatures in the range of from 700 to 800 F. The alloys of the present invention are especially useful in fabricating heat-transfer apparatus where the components must retain their strength and conductivity after being sub jected to an elevated temperature joining operation.

The high conductivity properties of the alloys of the present invention are not only unexpected, they are contrary to the teachings of the prior art. Technical SurveyOFHC Brand Copper, American Metal Co., Ltd. (1957), page 90, teaches that the addition of phosphorus or magnesium to copper increases the electrical resistivity, which results in decreased electrical conductivity of the alloy. The present invention, however, is directed to a copper alloy containing phosphorus and magnesium and exhibiting high conductivity properties.

These properties are obtained, it has been discovered, by controlling the amount of phosphorus relative to that of the magnesium present in the alloy; an alloy is produced which exhibits an electrical conductivity between 90 and 97% IACS. The optimum conductivity is achieved when the phosphorus is present in an amount equivalent to about 85% by weight with respect to the magnesium, i.e., a phosphorus-magnesium ratio of about 0.85 to :1. Moreover, the strengthening elfect of the magnesium on the tensile strength of the alloy is not materially diminished by the addition of phosphorus in an amount equivalent to about 85% of the magnesium. While cold working has a tendency to lower the electrical conductivity somewhat, as it does with copper alloys in general, the advantages obtained by controlling the ratio between the amounts of phosphorus and magnesium in the alloy as indicated above are also present in the cold-worked condition.

The unexpected properties exhibited by the present invention are believed to result from the formation of intermetallic compounds within the copper matrix.

It is believed that the phosphorus and magnesium combine to form an intermetallic compound approximating the formula Mg P or a complex mixture of compounds formed between copper, magnesium and phosphorus, such as Cu Mg and C11 1. The existence of a chemical interaction between the magnesium and the phosphorus is indicated by the fact that when phosphorus is added in an amount equal or close to the stoichiometric ratio of about 0.85 to 1, which exists between the relative weights of the phosphorus and the magnesium in the compound Mg 'P then the electrical conductivity reaches a peak value with the more simple thermo-rnechanical treatments such as those outlined in the subsequent Example 1. When the relative weight ratio of phosphorus to magnesium is materially less than or materially greater than 0.85 to 1, the electrical conductivity is also less than the 95-99% IACS peak value attainable using the aforementioned simple thermo-mechanical treatment. It is postulated that this decrease in conductivity is caused by the free phosphorus or magnesium which is in excess of the amount utilized in the formation of the intermetallic compound(s) and the free magnesium or phosphorus behaves as if it were alone in the copper and reduces the electrical conductivity accordingly. As discussed earlier, we have discovered that Cu-Mg-P alloys which also contain silver as an alloying element seem capable of producing a desirable combination of high conductivity and high tensile strength over a wider range of phosphorus-to-magnesium-ratios than in the absence of the silver.

The premise that the magnesium is reacting with the phosphorus is further supported by the fact that the presence of only phosphorus in the amount of 0.85% in pure copper increases the electrical resistivity of copper to a value of 2.90 microbm-cm. This resistivity is equivalent to only 59.5% IACS in electrical conductivity. (The resistivity of the International Annealed Copper Standard at 20 C. being 1.7241 microhm-cm.)

It has been founnd that in order to achieve electrical conductivity values of from 90% IACS to 99% IACS and to develop high mechanical strength at the same time, it is desirable to control the temperature and the time of the final annealing treatment. A good balance of properties is obtained by finally annealing the alloy at between about 700 to 1000 F. for from about one to about three hours. The alloy is then taken to its final dimensions by cold-working, e.g., cold-rolling, wiredrawing, swaging, cold-heading, etc. The increased properties are believed to be due to a combination of strength- '4 ening mechanisms including the coherency and the dispersion strengthening caused by the fine dispersion of intermetallic compound or compounds resulting from age-hardening (or precipitation-hardening), and cold work strengthening.

Thus it appears that, when silver is added to this alloy system, the precipitation mechanism is rendered more controllable, particularly as the strength and conductivity properties are affected by modifications in the thermomechanical processing. For example, with silver, the better combinations of strength and electrical conductivity can be attained over a somewhat wider range of alloy composition than in the absence of silver. Thus, alloys containing silver, e.g., .02 to .09% by weight can achieve high conductivity and mechanical strengths with the phosphorus-to-magnesium-ratio ranging from 0.3 to as high as 1.4.

In order to achieve these good results, it is necessary to vary the thermo-mechanical processing in some cases and this is usually more diflicult in the absence of silver. We have found that many thermo-mechanical processing variations can be used to give this alloy system a wide range of electrical conductivity and mechanical strength combinations and this versatility is one of the outstanding attributes of this Cu-Mg-P-base alloy. Techniques which are suitable include warm-rolling (pseudo-ausforming), zerolling, shock-loading, cryogenic cooling, stress aging, pseudo-maraging (quenching directly to the aging temperature from the solution-treatment temperature), multiple-aging treatments in succession at the same or various diiferent temperatures (with or without inter posing warm or cold-rolling in between the aging treatments), and various amounts of cold or warm-working prior to the aging treatment. The unifying feature of all these thermomechanical treatments is believed to be the efiect they have in establishing the size, shape, interparticle spacing, distribution, degree of coherency and other controlling characteristics of the precipitate particles. A majority of these precipitate particles (say in excess of 50%) are characterized by diameter less than 1 micron in extent.

To demonstrate the large effects that: prior thermomechanical processing, such as the amount of cold-work, has on final electrical conductivity two dilferent amounts of cold work, 69%, and 91%, were introduced into pre viously hot-rolled material, prior to receiving the precipitation-aging treatment. The results shown below indicate how higher electrical conductivity can be attained by increasing the amount of cold-work prior to the precipitation treatment for an alloy containing copper, .041% silver, .09% magnesium and .09% phosphorus.

Electrical conductivity after 3 hrs. at

800 F. precipitation-aging treatment, percent IACS Gauge, in. Percent cold reduction .160 69 (.500" to .160) .027 91 (.300" to .027") GENERAL DESCRIPTION OF THE DRAWINGS GENERAL DESCRIPTION OF THE INVENTION The present invention contemplates the production of unique low cost copper-magnesium-phosphorus alloys. Each of the alloys of this invention, after being subjected to appropriate thermo-mechanical processing has good electrical and thermal conductivity together with high mechanical strength, e.g., an ultimate tensile strength (UTS) in excess of 60,000 pounds per square inch (p.s.i.) despite elevation to temperatures of 700 F. or higher for about 3 minutes. Alloys within the contemplated scope of the present invention having the foregoing desirable properties and/or characteristics contain, in weight percentages, .002 to 4.25 phosphorus, 0.01 to 5.0 percent magneisum with the balance, apart from the usual impurities and residual elements, copper. In order to obtain optimum properties, the phosphorus and magnesium are employed in amounts sufiicient to establish a ratio by weight in the range of 0.3 to 1.3, preferably in the neighborhood of 0.85. The alloys of the present invention can also contain from 0.02 to 0.2 weight percent silver and from 0.01 to 2.0 weight percent cadmium.

Unlike comparable prior art alloys, the copper-base alloys of this invention can be produced from coppers containing by weight as much as 600 parts per million (p.p.m.), i.e., 0.06% of oxygen without materially and detrimentally altering the advantageous properties and/ or characteristics of these alloys. This is a very desirable economic advantage since it permits the use of the less expensive grades of copper in the manufacture of these alloys. Accordingly, tough pitch copper, which is a copper containing 0.02% to 0.05% oxygen and which is obtained by melting electrolytically obtained cathode copper or by fire refining, can be successfully used in producing the alloys of the present invention. Of course, it is to be appreciated that high purity, substantially oxygen-free coppers may also be employed in the manufacture of the alloys of the present invention if cost is not an important consideration. Thus, cathode copper is suitable starting material as is copper which has been produced in a reducing atmosphere such as OFHC brand copper (which is 99.99% or more pure), copper prepared in an inert atmosphere, under a charcoal cover or in a vacuum and chemically deoxidized coppers such as lithium-deoxidized copper. The use of pohsphorus deoxidized copper (DLP- deoxidized low phosphorus and DHP-deoxidized high phosphorus) is, of course, acceptable and in some cases preferable because it may eliminate the step of adding phosphorus to the copper if sufiicient phosphorus remains in solution in the copper.

The alloys of this invention containing the aforementioned ingredients, i.e., copper, phosphorus, magnesium and optionally silver or cadmium, in the aforementioned specially proportioned amounts are characterized by being cold-workable to strengths in excess of 60,000 p.s.i. These alloys are further characterized by having good castability.

Phosphorus is employed in an amount corresponding to from 0.002 to 4.25 weight percent of the total weight of the alloy. The phosphorus when employed in such amounts together with magnesium has a number of beneficial effects including alloying as well as deoxidizing effects. The magnesium is employed in amounts sufficient to constitute from 0.01 to 5.0 weight percent of the total weight of the alloy. The inclusion of magnesium has an important effect upon the unexpected tensile strength and electrical and thermal conductivity properties of the alloy. The optimum balance of mechanical and electrical and thermal conductivity properties is obtained when the phosphorus and magnesium are employed with respect to each in a weight ratio of about 0.85 to 1. When employed in proportions substantailly equivalent to this ratio, the phosphorus and magnesium have a synergistic effect on the thermal and electrical conductivity and on the mechanical properties. Material deviations from this ratio may result in a decrease in the strength of the alloy, a decrease in the thermal and electrical conductivity or a decrease in both properties although in most cases this tendency can be counteracted by appropriate changes in the thermo-mechanical processing; also, as noted else- 6 where, the presence of silver minimizes this decrease. It has been found that increasing the proportion of phosphorus with respect to the magnesium has a greater deleterious effect on the properties of the alloy than increasing the proportion of magneisum with respect to the phosphorus. When the magnesium content of the alloy is from 0.01 to about 0.5 weight percent, the desired strength and conductivity properties are obtained without using special processing; however, when the amount of magnesium is in excess of 0.5 weight percent, special thermo-mechanical processing steps are recommended to obtain optimum properties. The special thermo-mechanical processing steps are believed to be made necessary by the relatively large amount of intermetallic compound of compounds present in the copper matrix.

Such versatility and good control of a wide range of desirable properties has long been sought and, until the present discovery, has eluded metallurgists. While the atomistic mechanisms which effect the excellent combinations of properties achieved by this discovery have not yet been completely elucidated, the following hypothetical model will be instructive to those skilled in the art and will assist them in the practice of the invention:

(A) At temperatures above about 1200-1400 F., it appears that P and .Mg go into solid solution to the extent of their solid solubility in Cu at the solution annealing temperature employed.

(B) It appears further that both P and Mg tend to stay in solid solution even when the temperature is lowered so that the solid solution state becomes a nonequilibrium condition rather than to precipitate out readily as Cu Mg and Cu P, respectively. Thus, rapid cooling such as water quenching, or even air cooling, maintains a substantial part of all, of the P and Mg in solid solution. This gives low conductivity and solid solution strengthening. When this super-saturated solid solution structure is cold worked, quite high strengths are obtained eg the 90,000 p.s.i. ultimate tensile strength (and 70% IACS). This cold working does not appear per se to cause precipitation of Cu-Mg and Cu-P compounds but it does condition the copper matrix to precipitate such compounds if thereafter the material is heated; additional cycles of cold working and elevated tempera tures aging further promote the precipitation of such compounds.

(C) -In order to secure high conductivities, e.g. 99% I'ACS, rather than the 70% IACS noted above, it is necessary to precipitate the Mg and P from solid solution. As indicated above in paragraph (B) the binary equilibrium diagrams of Cu-Mg and of Cu-P suggest that these precipitations might be Cu Mg and Cu P. The precipitation may, however, be a complex of these or other compounds. Moreover, as is well 'known in the case of carbide compounds in tool steels where simple carbides precipitate first then by interdiffusion form very complex carbides during tempering, two or more compounds may form separately and then subsequently may form the final precipitation-this is particularly true in the alloys of this invention where Ag and/or Cd may advantageously be present to modify the kinetics and/or compositions of the precipitations. The alloys of this invention thus are characterized by a relatively controlled rate of precipitation. This is very fortunate: standard, low-cost rolling and heating schedules for which existing production equipment is well-adapted can be employed while maintaining the Mg, P, Ag and/or Cd in solution; then, again by standard, low-cost processing in existing production equipment, a metallurgist skilled in the art and following the teachings of this specification can select optimum combinations of strength and conductivity by starting at the high strength made possible by the solid solution plus cold work and gradually, under excellent production control, can increase the conductivity by suitable thermo-mechanical processing. The atomistic mechanism for this is controlled precipitation of compounds made possible by the critical amounts and ratios, as taught herein, of Mg, P, Ag and/or Cd in conjunction with appropriate thermo-mechanical processing. This controlled precipitation yields a most important benefit, surprisingly high in its degree of effectivenesshigh resistance to softening by heat as noted in the following paragraph (D).

(D) A first factor resides in the fact that fundamentally, Cu contributes high conductivity and high cold-workstrengthenability. Mg and P, optionally with Ag and/or Cd, first contribute an important increase in the coldwork-strengthenability of Cu via solid solution but at some cost in conductivity; then, within the critical limits taught herein, the Mg, P, Ag and/or Cd can be precipitated under excellent control to give a dispersion of precipitate particles throughout the Cu matrix above the softening temperature of the Cu matrix-thus the cold work-strengthening is sacrified while the conductivity is increased by precipitating the Mg, P, Ag and/or Cd out of solid solution. A second factor resides in the discovery that the matrix containing the precipitate can now be cold-worked to regain the cold-work strengthening with only a small loss of electrical conductivity. The matrix containing the precipitate work-hardens at a more rapid rate than the solution-annealed and quenched alloy, and, therefore, higher strengths may be obtained for an equivalent amount of cold work. A third factor resides in the discovery that the precipitate so formed now inhibits the atomic movements which are necessary to dissipate coldwork-strengthening i.e. the precipitate particles block recrystallimtion and softening. The result is that the properly processed alloy can, without serious or complete softening, be heated and used at temperatures and time considerably higher than any hitherto known material with comparable conductivity and strength.

Silver when present in the amounts hereinbefore set forth, i.e., 0.02 to 0.2%, together with proper amounts of magnesium and phosphorus (whether cadmium is present or not) as previously mentioned, has a number of beneficial elfects upon the mechanical and conduction properties. In addition to greater latitude in permissible P to Mg ratios, noted earlier, silver raises the softening temperatures and increases the strength of the alloy. Secondly, silver retards recrystallization of wrought copper significantly. T hirdly, it is believed that silver inhibits grain growth. Further, the desirability of the silver in the aforementioned ranges permits the use of the base-copper containing silver such as Copper Range White Pine silver-bean'ng coppers, when making the alloys of the present invention, and these commercially available grades of copper can be used without sacrificing such desirable properties and/or characteristics as electrical or thermal conductivity.

As pointed out hereinbefore, the alloys of this invention may contain up to 2.0% cadmium by weight. The addition of cadmium to the copper-magnesium-phosphorus or copper-magnesiurn-phosphorus-silver alloys of the invention results in the retention of strengths higher after exposure to elevated temperatures without detrimentally decreasing the conductivity and/or the mechanical properties for many important commercial applications.

In carrying the invention into practice, particularly significant results are obtained when the alloys contain approximately in weight percentages, 0.05 to 0.3% magnesium, 0.04 to 0.25% phosphorus, 0.03 to 0.09% silver and 0.02 to 0.10% cadmium, with the balance, apart from the usual impurities and residual elements, copper. Such alloys have a superior combination of physical, mechanical and/or metallurgical properties and/or characteristics in combination with being inexpensively produced.

Alloys within the broad and advantageous ranges are resistant to thermal softening after they have been subjected to cold-working operations. Advantageously, the

alloys are cold-worked at least 40% to obtain greater strength and hardness. More advantageously, they are cold-worked at least 60 to As those skilled in the art Will readily appreciate, the softening temperature is a function of the amount of cold work, to wit, the lower the amount of cold work, the higher the softening temperature, and conversely. In any event, the half-hardness temperature of the cadmium-free alloys of this invention lies between 725 F. to 750 F. When cadmium is present in the amounts heretofore mentioned, the half-hardness temperature for 30 minutes is between about 750 and 800 F.

The unique copper-magnesium-phosphorus and copper-magnesium-phosphorus-silver alloys of this invention are prepared in accordance with known procedures. In representative operations, the copper is melted and the alloying ingredients added thereto. The melting of the copper can be carried out in air under a protective cover or in a vacuum. Special refractories such as aluminum oxide, magnesium oxide and the like can be employed in the production of the alloy. It is advantageous, particularly when using tough pitch or other relatively high oxygen containing coppers, to add the phosphorus before or simultaneously with the silver and the magnesium or cadmium to be added after the deoxidation in order to magnesium and cadmium losses. The established melt is then preferably cast in a non-oxidizing atmosphere such as N or argon.

It is advantageous, particularly because of the small amounts used, to add, in terms of weight percent, the magnesium as a copper-10 to 20% magnesium alloy, phosphorus as 15% phosphorus-copper and cadmium as a copper-5% cadmium alloy. Silver may, on the other hand, be added in the elemental form or as a master alloy.

The alloys of the present invention can be worked using a variety of techniques. Good balance between the mechanical and conductivity properties of the alloys containing from about 0.01 to about 1 weight percent magnesium and from about 0.002 to 0.85 weight percent phosphorus (with or without silver and cadmium) is obtained when the alloys are worked as follows. Cast rolling slabs are hot-rolled at temperatures from about 1000 to 1600 F. to a metal thickness of about 0.30 to 0.50 inch. Further reduction in thickness is achieved 'by conventional cold-rolling and annealing procedures. In fact these alloys can be intermediately annealed in the readily available continuous annealing lines.

In those alloys where the magnesium and phosphorus are present in amounts equivalent to from about 1.0 to about 2.0 and from about 0.85 to about 1.70 Weight percent, respectively, good mechanical and conductivity properties are obtained by deforming the primary cast ingot structure by h0t-f0rging operations at temperatures between 1200 and 1400 F. Following the initial hotforging steps additional reduction is carried out by coldworking.

When employing an alloy having a magnesium and phosphorus content of from about 2.0 to 5.0 and about 1.7 to about 4.25 weight percent, respectively, a wrought product is produced by reducing the cast blank or intermediate at a temperature below about 1200 F. in order to avoid rupturing the cast blank.

It is, of course, understood that the alloys of the present invenhion can be sold in the as-cast state or after any degree of reduction (hot or cold). They can also for some applications he produced and processed by power metallurgical techniques. The fabricator can then age-harden and/or work-harden the material at the desired stage in his fabrication procedure.

The adaptability of these alloys for producing high electrical conductivity and hardness from an as-cast condition, or from an as-cast and solution-annealed condition, by means of a simple precipitation heat treatment is shown by the data below for an alloy containing copper 9 with 0.041% silver, 0.16% magnesium, and 0.148% phosphorus, which was aged at 800 F. for the times indicated.

Aging time at 800 F.

'2 hours at 1,400 F.

SPECIFIC EXAMPLES The following examples are merely illustrative and are not deemed to be limiting.

Example 1 The alloys of the present invention having the composition set forth in Table I were prepared by melting ETP copper, at about 2000 F. Carbon was added to the melt to deoxidize the copper partially. Fifteen percent phosphorus-copper was then added to the melt to complete the deoxidization of the copper; however, enough phosphorus must be added to provide, after the deoxidation is complete, an amount of phosphorus equivalent to the desired phosphorus content of the alloy. Following the addition of the phosphorus-copper, the magnesium was added to the melt in the form of a copper-magnesium alloy containing about 10 percent magnesium. (The silver, if not already present, is added before or after the deoxidizing process. It is, of course, possible and convenient to use a. copper which already contains silver.) The entire melting and compounding process was carried out under an atmosphere of nonoxidizive protective gas such as nitrogen or the like. The

10 drawings. Referring now thereto, the drawing is a perspective view, partially broken, of a typical fin and tube type radiator assembly having a plurality of large surface area fins 22 or heat transfer surfaces and coolant tubes 20 for water passage.

The reason for the strength requirements stems from the amount of handling, particularly during assembly and installation, to which the apparatus is subjected coupled with a requirement that the fins be quite thin. Being so thin, they must be strong enough to resist the multiple stresses to which they 'are subjected during fabrication, installation and use. In addition, the strength as well as the conductivity requirements take into effect the temperature at which the soldering operation is conducted.

FIG. 2 illustrates a pair of metal sheets 24, 26 being spot welded as at 28 by a pair of welding tips 30, 32, composed of a copper alloy of the present invention. FIG. 3 illustrates a pair of metal sheets 34, 36 being resistance welded along a seam 38 by a pair of Welding wheels 40, 42, composed of a copper alloy of the present invention. FIG. 4 illustrates a coiled compression spring 44, composed of copper alloy of the present invention.

Example 2 In further operations, other alloys of the present invention are prepared. These alloys are prepared from ETP copper as described in Example 1. Each alloy thus prepared is hot-rolled at 1450 F. and reduced from 1 inch to /2 inch. The /2 inch material is placed in the annealing furnace for 30 minutes at 1450 F. and then water-quenched. The water-quenched material is coldrolled percent to produce a A inch strip which was cold-rolled further (85%) to obtain a strip 0.024 inch thick. This strip is annealed at 750 F. in molten salt for from 10 to 30 minutes, and then cold-rolled again (SW/2%) to obtain a strip 0.003 inch thick. This strip is made into tensile samples and tested as cold-rolled and after a 3-minute anneal at 710 F. (in molten salt). The composition of these alloys and their properties are melt was poured into cakes while at a temperature of 40 listed in Table II.

TABLE I Tensile strength and electrical conductivity in as-rolled (90%) stri2r7! .003 thick after receiving the following annealing conditions at .0

Annealing tempera- Annealing temperature, 1,000 F. for ture, 800 F. for 3h0urs 3hours Composition, weight percent UTS Percent UTS Percent Ag Mg P On (KIPS) IACS (KIPS) IACS 0. 041 0. 1 008 Remainder 61. 5 88 78. 1 87 0. 041 0. 1 024 d 76. 6 90 75. 8 s7 0. 041 0. 1 75. 7 00 77. 0 00 0. 041 0. 1 76. 4 91 76. 0 89 0. 041 o. 1 74. 9 90 81. 9 89 0. 041 0.1 76. 6 93 so 5 92 0050" thick strip (cold-rolled 69%). about 2150 F. Cakes of each alloy were then hot-rolled TABLE II at a starting temperature of 1500 F. to 0.30 inch and Ultimatetensfle allowed to cool to room temperature. The 0.300 lHCh strength (psi) strip was then scalped to 0.285 inch and thereafter cold- Composflwn 907 annealed rolled to 0.0275 inch. This 0.0275 inch strip was then Mg P on AS rolled g g 7100F O O annealed at from 800 to 1000 The anneahng or 05 .008 Remainder" 78,000 65,000 aging, cycle was three hours heatlng, three hours at .105 .008 do 86,000 68,000 temperature and six hours cooling to room temperature. 90,000 69,000 77,000 04, 000 The 0.0275 lnCh strip was finally cold-rolled 90% to 84,000 67,500 0.003 inch. The strips thus produced were tested to de- 5883 32.88% termine their ultimate tensile strength. Electrical con- 361000 68: 000 ductivity (percent IACS) was determined on strips which 33 888 22 388 were cold-rolled to a thickness of 0.050 inch. The re- 721000 001000 sults of these test are tabulated in Table I. 1 68,000

As was pointed out hereinbefore, there is a demand for a low cost copper alloy which will retain a UTS of 50,000 to 60,000 p.s.i. and a conductivity of at least 90 percent IACS after exposure to a temperature of 800 F. for 3 minutes. One use for such an alloy is its employment as the structural material for heat transfer fins for automobile and other vehicle radiators as exemplified by the radiator assembly depicted in FIG. 1 of the Example 3 In order to illustrate the novel and desirable effects due to the inclusion of cadmium in the alloys of the present invention, alloys X and Y were prepared in the same manner as the alloys described in Example 1. These alloys were prepared as a 0.10 inch strip which had been cold-worked percent prior to being heated 11 in a salt bath at 710 F. The strip was then tested for hardness. The results which show the retention of the as-rolled hardness, which is indicative of the strength, are listed below in Table III.

TABLE III Hardness, Rockwell B After heating* Composition, percent As- 3 90 Alloy Ag Mg P Cd Cu rolled min. min.

X656)--- .043 .05 0.1 .02 Remainder 70 71 74 Y(557)-- .043 .13 0.1 02 o 74 82 81 In molten salt at 710 F.

Example 4 An alloy having a composition of 0.041% silver, 0.53% magnesium, 0.32% phosphorus. with the remainder being copper was cast into 1-inch thick slabs for hot-rolling in accordance with the method of Example l. The alloy was hot-rolled at 1650 F. from 1 inch to 0.480 inch with reheat after each pass, and water-quenched from 1650 F. Cold-rolling was then carried out to reduce the strip 68% from 0.48 inch to .160 inch. Very good retention of hardness is possessed by this alloy as indicated when the alloy is heated at 700 F. for 200 minutes, and shown by the data below.

(1)Hot-rolled from 1" to 0.480", water quenched from 1650" F., then cold-rolled 68% from 0.480 to 0.160" 84.5 (2) Aged at 700 F. for the following times:

3 minutes 94.0 minutes 95.0 50 minutes 92.0 100 minutes 91.0 200 minutes 92.0

CONCLUSION Thus the additives of the present invention do not appreciably adversely afiect two basic properties of pure copper, viz, high conductivity, both electrical and thermal; and (2) high strengthenability by cold work with very little loss in conductivity, e.g. only a drop from 100% IACS to 97-98% IACS by 60-90% cold reduction, which can increase the yield strength by a factor as high as five and can more than double the ultimate tensile strength. Moreover, employing two of the lowest-cost and most abundant elements-phosphorus and magnesiumwithin critical percentage ranges and in critical ratios, four important objectives are accomplished at will and under good control:

(1) Achieving high strength with good conductivity e.g. 90,000 p.s.i. ultimate tensile strength (compared to a pure Cu maximum of 65,000-70,000 p.s.i.) with 70% IACS;

(2) Achieving moderate strength, even after elevated temperature fabrication such as soldering for 3 minutes at 800 F. with excellent conductivity e.g. 55,000 p.s.i. ultimate tensile strength (compared to a pure Cu, or even a silver-bearing copper, maximum of 30,000- 35,000 p.s.i.) with 95% IACS;

(3) Combinations of strength and conductivity intermediate between (1) and (2) above; and

12 (4) Higher resistance to heat softening as described above.

Since certain changes may be made in the above disclosure Without departing from the scope of the drawings herein, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted in an illustrative and not in a limiting sense.

What is claimed is:

1. A copper base alloy material consisting essentially of by weight 0.002 to 4.25 percent phosphorus, 0.01 to 5.0 percent magnesium with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

2. A copper base alloy material consisting essentially of by weight 0.002 to 4.25 percent phosphorus, 0.01 to 5.0 percent magnesium, 0.02. to 0.2 percent silver with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

3. A copper base alloy material consisting essentially of by weight 0.002 to 4.25 percent phosphorus, 0.01 to 5.0 percent magnesium, 0.02 to 0.2 percent silver, up to 2 percent cadmium with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

4. The copper base alloys claimed in claim 1 wherein the phosphorus and magnesium are employed at a ratio of from 0.85 to 1.00 by weight.

5. A copper base material consisting essentially of from 2 to 5 percent magnesium, from 0.6 to 4.25 percent phosphorus with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

6. A copper base material consisting essentially of from 1.0 to 2.0 percent magnesium, from 0.3 to 2.0 percent phosphorus with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

7. A radiator fin comprised of the copper material claimed in claim 1.

8. An electrical conductor comprised of the copper material claimed in claim 1.

9. A copper-base material consisting essentially of from 0.01 to 1.0 percent magnesium, from 0.003 to 1.0 percent phosphorus with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

10. A copper-base material consisting essentially of from 0.01 to 1.0 percent magnesium, from 0.003 to 1.0 percent phosphorus, 0.02 to 0.2 percent silver with the remainder being copper, the approximately stoichiometric ratio of phosphorus to magnesium ranging from 0.3 to 1.4 by weight.

References Cited UNITED STATES PATENTS 2,123,628 7/ 1938 Hensel et al. -153 2,171,697 9/ 1939 Hensel et al. 75-153 2,243,276 5/1941 Hensel et al. 75-153 2,268,938 1/ 1942 Hensel 75-153 FOREIGN PATENTS 577,850 6/1959 Canada 75-153 915,392 7/1954 Germany 75-153 CHARLES N. LOVELL, Primary Examiner US. Cl. X.R. 148-325 

